Coffee Extraction Calculator

How It Works

Coffee extraction is the fraction of the dry coffee bean's mass that ends up dissolved in the brewed beverage. From the Specialty Coffee Association's Coffee Brewing Handbook, the two key numbers are TDS (Total Dissolved Solids, the percentage of the brewed coffee's mass that is dissolved solids) and extraction yield (the percentage of the original dry coffee that ended up in the cup). The relationship:

Extraction yield = TDS × Beverage weight / Dose

For a V60 pour-over with 22 g dry coffee dose, 360 g brewed weight, and a TDS reading of 1.42%: extraction = 0.0142 × 360 / 22 = 23.2%. That's just above the SCA Gold Cup zone of 18-22% — a lightly over-extracted cup, likely to taste slightly bitter.

The Gold Cup zone — 18-22% extraction with 1.15-1.35% TDS — comes from Ernest Illy's 1950s taste-panel research, formalized in the SCA handbook and refined by Emma Sage's "Refractometer-Based TDS Measurement" technical papers. The zone represents the extraction range where most tasters find coffee balanced (not sour, not bitter). Coffees outside the zone can still be enjoyable — many light-roast pour-overs push to 23-24% extraction with fruit-forward beans — but the zone is the safe default for a first cup.

TDS is measured with a refractometer that reads a few drops of brewed coffee at 20 °C. Consumer refractometers (VST Coffee Tools, Atago) read TDS to ±0.05% accuracy. Cheaper refractometers can drift by 0.1-0.2%, which shifts calculated extraction by 1-2%. VST's calibration methodology (vstapps.com/calibration) documents how to correct for meter-to-meter differences.

How to Use This Calculator

1. Weigh dry coffee dose — in grams, before brewing. Common ratios are 22 g coffee for a pour-over V60 or 18 g for a double espresso.
2. Weigh brewed beverage — in grams, after brewing. For V60 this is the liquid in the cup; for espresso it's the shot in the receiving cup.
3. Measure TDS with refractometer — two or three drops of brewed coffee at 20 °C. Wipe the sensor between readings.
4. Enter dose, beverage weight, and TDS — the calculator computes extraction yield, brew ratio, and the SCA Gold Cup zone comparison.
5. Read the extraction yield — reported as a percentage. 18-22% is the Gold Cup zone; below is under-extracted, above is over-extracted.
6. Adjust grind and brew time — follow the calculator's recommendation: grind finer for under-extracted, coarser for over-extracted, or adjust brew time as a secondary lever.

Real-World Use Cases

V60 pour-over

A home barista brews a V60 with 22 g coffee to 360 g brewed weight and reads TDS 1.42%. Extraction = 0.0142 × 360 / 22 = 23.2% — just above the Gold Cup ceiling. The tool suggests grinding one click coarser to drop into the 20-22% target range. Next brew at the coarser setting reads TDS 1.35% and extraction 22.1% — Gold Cup.

Espresso ratio check

A café dials in a 1:2 espresso (18 g dry coffee in, 36 g shot out) with TDS 10.5%. Extraction = 0.105 × 36 / 18 = 21.0% — in the Gold Cup zone for espresso. The barista compares this to the shop's target extraction (typically 20-22% for espresso) and confirms the setup is on-spec. If the shot tasted sour, the fix would be a finer grind to push extraction higher.

Diagnosing sourness

A brewer complains that his pour-overs taste sour. He measures: 20 g dose, 320 g brewed, TDS 1.05%. Extraction = 0.0105 × 320 / 20 = 16.8% — well below the Gold Cup floor. Under-extracted coffee is sour because acid compounds come out first and sugar/body compounds haven't come out yet. Fix: grind finer or extend brew time. He grinds two clicks finer, next brew reads 1.28% TDS and 20.5% extraction — balanced.

Tips & Safety Notes

• Weigh everything, don't scoop. A ±5% dose error shifts extraction by roughly the same percentage. Use a scale accurate to 0.1 g.
• Filter your brew water. Very hard water (>200 ppm TDS) extracts differently than filtered water and shifts the calculator's TDS reading downward. SCA recommends 75-150 ppm total hardness.
• Take the TDS reading at 20 °C or apply temperature correction. Refractometer readings drift about 0.02% per degree from calibration temperature.
• Wipe the sensor between readings. A stray drop from the previous cup can shift the reading by 0.1% or more.
• Fresh beans matter. Coffee more than 3 weeks post-roast loses gas retention and extracts differently — a formerly Gold Cup grind can drift outside the zone as the beans age.

Limitations & What This Tool Cannot Do

• TDS meter accuracy. Consumer refractometers have ±0.05% precision; extraction yield is sensitive to TDS input, so an inexpensive meter can shift the calculated number by 0.5-1% extraction. Use a calibrated VST-grade meter for shop-critical work.
• Refractometer vs meter. The tool accepts TDS from either device; both use different scales and slight assumptions differ. If your device outputs "Brix" instead of "TDS," a conversion (roughly TDS = Brix / 0.85 for coffee) is needed — the calculator has a toggle for this.
• Only reports the number. Extraction yield is a diagnostic tool, not a flavor predictor. It tells you if the coffee is under- or over-extracted, but not whether that specific bean at that specific extraction will taste good — flavor depends on bean origin, roast level, freshness, and water chemistry that the extraction number alone cannot capture.

FAQ

What is TDS (Total Dissolved Solids) and how is it measured?

TDS is the percentage of the brewed coffee's mass that is dissolved coffee solids — the sugars, acids, and flavor compounds pulled from the grounds. It is measured with a refractometer that reads a few drops of brewed coffee at 20 °C. Consumer refractometers (VST, Atago) read TDS to ±0.05% accuracy.

What is the SCA Gold Cup extraction range and where does it come from?

The Specialty Coffee Association's Gold Cup zone is 18-22% extraction yield with 1.15-1.35% TDS. It comes from Ernest Illy's 1950s taste-testing work formalized in the SCA Coffee Brewing Handbook. Coffee brewed inside this zone tastes balanced and clean; outside it, you get sourness (under-extracted) or bitterness (over-extracted).

Why do the same beans taste different at different extraction yields?

Different flavor compounds dissolve at different rates. Acids and bright aromatics come out first (under-extracted coffee tastes sour). Sugars and body compounds come out in the middle (18-22% is where the balance sits). Bitter compounds come out last (over-extracted coffee tastes bitter). The extraction curve is the same for all beans; the beans differ in what balance you prefer.

Does grind size or brew time have more impact on extraction?

For pour-over and drip, grind size dominates because it changes the surface area exposed to water. For espresso, pressure and time interact more with grind. General rule: to raise extraction, grind finer first; if you cannot go finer without over-extracting other compounds, add brew time. Grind size is the more responsive lever.

What is a "channeling" defect and how do I recognize it in the numbers?

Channeling is when water flows through a preferred path in the coffee bed instead of evenly wetting all the grounds. You see it as lower-than-expected TDS at a given brew ratio, combined with a coffee that tastes sour and bitter at the same time (some grounds are under-extracted, others over-extracted). Fix by improving distribution before brew and eliminating high-flow spots on the coffee bed.

Do I need a refractometer to use this calculator, or can I estimate TDS?

A refractometer gives ±0.05% TDS accuracy and is worth the ~$150 investment if you brew coffee daily. Without one, you can estimate TDS from a rough taste category (weak ~1.0%, balanced ~1.2%, strong ~1.4%) and get extraction to ±2%. That's enough to tell you if you're 15% or 22% but not to fine-tune between 20% and 22%.

Related Tools

• Brewing ABV Calculator — Adjacent brewing analytics
• Sourdough Hydration Calculator — Adjacent ferment math
• Charcuterie Cure Calculator — Adjacent food-science

References

• Specialty Coffee Association (SCA) Coffee Standards and the SCA Coffee Brewing Handbook — Gold Cup extraction and TDS ranges, taste-panel methodology
• Emma Sage, "Refractometer-Based TDS Measurement," SCA technical papers — measurement protocols and meter-to-meter variability
• VST Coffee Tools calibration methodology (vstapps.com/calibration) — refractometer calibration procedures

Reviewed by the Craft Calc Lab team on August 4, 2026.